@article{700176,
     title = {Spectral analysis of non-self-adjoint elliptic operators},
     booktitle = {Equadiff 6},
     series = {GDML\_Books},
     publisher = {J. E. Purkyn\v e University, Department of Mathematics},
     address = {Brno},
     year = {1986},
     pages = {[197]-202},
     mrnumber = {MR0877124},
     zbl = {0614.35064},
     url = {http://dml.mathdoc.fr/item/700176}
}

Brilla, Jozef. Spectral analysis of non-self-adjoint elliptic operators, dans Equadiff 6, GDML_Books,  (1986), pp. [197]-202. http://gdmltest.u-ga.fr/item/700176/